1. Field of the Invention
The present invention relates to a planographic printing plate machining device, a planographic printing plate machining method and a planographic printing plate, and more particularly, concerns a planographic printing plate capable of improving the appearance of a surface of printed paper, and a planographic printing plate machining device and planographic printing plate machining method for providing such a planographic printing plate through a machining process (in particular, machining at edge portions).
2. Description of the Related Art
In general, a photosensitive planographic printing plate (hereinafter referred to as a xe2x80x9cPS platexe2x80x9d when appropriate) is manufactured through processes in which a support member, such as an aluminum plate in a sheet shape or a coil shape, is subjected to one or an appropriate combination of surface processes such as graining, anode oxidation, silicate processing and other chemical processes and the like, further subjected to coating of a photosensitive liquid and a drying process, and then cut to a desired size. This PS plate is further subjected to plate-forming processes such as exposure, development, gumming and the like, set in a printing press, and coated with ink. Thus, characters, images, etc. are printed on a surface of paper.
Printing using such a PS plate may be printing on printing paper that has a size smaller than the size of the PS plate using a general commercial printing press, and may be printing on printing paper that has a size larger than the size of the PS plate, such as, when printing newspapers and the like. In the latter case, because the entire surface of the PS plate is used as a printing surface, ink adhering to cut edges (peripheral portions) of the PS plate may be printed on the printing paper, resulting in stains and consequently reducing commercial value of printed matter.
With respect to methods for preventing such stains adhering to the surface of printing paper due to unnecessary ink on the PS plate, for example, Japanese Patent Application Publication (JP-B) No. 57-46754 discloses a method in which corners of the edges of an aluminum support member are trimmed with a file or a knife, and JP-B No. 62-61946 discloses a method in which insensitive oil is applied to cut edge surfaces.
Further, as disclosed in Japanese Patent Application Laid-Open (JP-A) No. 62-19315, burrs caused during cutting are one of the causes of such stains and thus there are methods for preventing burrs from occurring at the printing surface side. Furthermore, JP-A No. 7-32758 has proposed shaping in which the cut edges are bent toward a side opposite the printing surface and consequent improvements can be seen.
However, in the method of trimming corners of edge portions of the support member with a file or a knife, PS plates have to be taken out one by one to be trimmed. Therefore, this method is not appropriate for use in bulk processing. When there are defects, such as burrs and scratches, that cause adhesion of ink is caught at trimmed portions, and may eventually cause stains on the surface of printing paper. Further, in the method of applying an insensitive oil to the cut edge surfaces, PS plates may stick to each other, causing difficulty in handling, and development failures may occur.
Moreover, depending on printing conditions, stains may still appear if burrs are simply not caused to occur at the printing paper surface side during cutting. Furthermore, a shape in which the cut edge portions are bent downward (toward the side opposite the printing surface) tends to improve staining but may be a cause of transport failures, such as snagging problems, during transportation at a printing plate forming device that performs exposure and development.
In order to solve the above-mentioned problems, a method has been proposed in which, when a PS plate is sheared with a slitter, cutter, etc., a cutoff is effectively formed at each edge corner portion of a surface treatment layer, at the same time as shearing, by using so-called shearing drops. This method has been respectively disclosed in: JP-A No. 5-104871, JP-A No. 8-11451, JP-A No. 9-53465, JP-A No. 9-323486, JP-A No. 10-35130 and JP-A No. 10-100566 and the like.
However, if cutoffs that are effective for preventing stains on the printing paper surface are formed by shear processing using slitters, cutters and the like, large burrs may occur at a rear surface (a surface opposite the surface at which the surface treatment layer is formed). When these burrs protrude from the rear surface, problems such as, the PS plate meandering while being transported in an exposing device or the burrs falling off and becoming garbage occur. Moreover, at the time of shearing, large cracks may occur at the front surface (the surface at which the surface treatment layer is formed), which affects the printed matter.
In order to solve the above-mentioned problems, a method has been proposed in which such a machining operation is carried out in a coil manufacturing process. For example, cutoffs are formed in a step prior to formation of the surface treatment layer at the support member. However, in this manufacturing method, processing must be done after setting the coil width for each size of the PS plates. In particular, if the PS plates have a large number of sizes, it is difficult to set the coil width for each size. Moreover, pluralities of PS plates may be formed from an elongated web in a width direction thereof but the above-described method is capable of producing only one PS plate in the width direction of the web, resulting in a reduction in manufacturing efficiency.
The present invention has been devised to solve the above-described problems and its object is to provide a planographic printing plate which has smaller burrs generated at a rear face and has a cutoff portion having a sufficient size at a surface, and a planographic printing plate machining device and a planographic printing plate machining method for forming such a planographic printing plate by cutting.
In a first aspect of the present invention, the planographic printing plate machining device of the present invention is provided with a pressing member which presses and indents a planographic printing plate from the printing side surface, thereby forming a recessed section that has a sloped face which continues from the printing side surface; and a cutting member for cutting the planographic printing plate.
When a planographic printing plate is machined using this planographic printing plate machining device, first, the planographic printing plate is pressed by the pressing member from the surface, with the result that a recessed section having a sloped face which continues from the surface and slants with respect to the surface is formed. Then, the cutting member cuts the planographic printing plate along this recessed section. Therefore, one portion or the whole of the sloped face formed by the pressing member is allowed to remain at the planographic printing plate after cutting, and this remaining sloped face effectively forms a cutoff portion.
Hence, since formation of the cutoff portion and cutting of the planographic printing plate are carried out using separate respective members, it is not necessary to generate a shearing drop to form a cutoff portion at a time of cutting. Therefore, the planographic printing plate can be cut under conditions that make smaller shearing drops at the time of cutting smaller, thereby making reduction of burrs (or more preferably, elimination of burrs) possible. Moreover, because the pressing process is positively done by the pressing member, a cutoff portion having a required size can be formed easily. In particular, even in the case of a planographic printing plate covered with a surface treatment layer containing, for example, an anode oxidation layer, it is possible to form a cutoff portion having a required size.
In the present invention, xe2x80x9ccuttingxe2x80x9d refers to cutting process that passes through a planographic printing plate in a plate thickness direction at a predetermined position. For example, this includes any cutting, such as cutting the web of an elongated planographic printing plate along a width direction, or for cutting such an elongated web in a length direction (so-called shearing) and cutting in a diagonal direction.
Moreover, the position of cutting of the planographic printing plate by the cutting device may be any position within the recessed portion, and is not limited to the sloped face of the recessed portion. For example, in a case wherein a flat face which is parallel to the surface of the planographic printing plate is formed continuously with the sloped face (therefore, the flat face also forms the recessed portion), the planographic printing plate may be cut at this flat face.
In a second aspect of the present invention, the pressing member is provided with a pressing portion extending in a direction substantially parallel with the printing side surface of a planographic printing plate, for pressing the planographic printing plate from the printing side surface; and a sloped portion that is slanted with respect to the printing side surface of the planographic printing plate so as to form the sloped face when the pressing portion presses the planographic printing plate.
In this aspect, because the pressing portion presses the planographic printing plate from a surface side, the planographic printing plate is positively indented to form the recessed portion. Moreover, as the pressing portion presses the planographic printing plate, the sloped portion forms the sloped face at the planographic printing plate. Because the shape of the sloped face (i.e. cutoff) is determined by the sloped portion, a sloped face having a desired shape can be formed by modifying the shape of the sloped portion.
In a third aspect of the present invention, the pressing member is provided with the pressing portion includes a contact section that contacts the printing surface side of the planographic printing plate, when the pressing portion presses the planographic printing plate and the sloped portion forms the sloped face.
In this aspect, when the pressing member presses the planographic printing plate, the contact portion is allowed to contact the surface of the planographic printing plate so that it is possible to prevent lifting of the planographic printing plate, positional offset, etc.
In a fourth aspect of the present invention, a supporting member which supports the planographic printing plate is further provided, the recessed section being formed by sandwiching the planographic printing plate between the support member and the pressing member, and the cutting member includes a cutting blade which cuts the planographic printing plate between the cutting blade and said supporting member.
In other words, the pressing member and the cutting member have the supporting member as a component in common. Consequently, the cutting member can be positioned and made to cut with high precision with respect to the recessed section formed by the pressing member. Moreover, since the supporting member is used in common, the number of constituent parts forming the planographic printing plate machining device is reduced.
In a fifth aspect of the present invention, the planographic printing plate machining device is provided with a shearing press blade formed to integrally include: a cutting blade section that is capable of cutting the planographic printing plate, thereby forming a cut edge portion; and a recessed section forming section which presses the cut edge portion so as to form a recessed section in the planographic printing plate.
In this aspect, the cutting blade section cuts the planographic printing plate, and the recessed section forming section presses the cut edge portion of the planographic printing plate, thereby obtaining a planographic printing plate in which a desired cutoff is formed. Here, the cutting blade section and the recessed section forming section function as the cutting member and the pressing member in the first feature. In other words, in accordance with the present aspect, the shearing member and the pressing member are formed into one shearing press blade. Thus, it is possible to improve machining precision at a time of machining, and also to reduce the number of parts required for machining.
In a sixth aspect of the present invention, the planographic printing plate machining device is further provided with an expansion permission section, which permits expansion of the planographic printing plate caused by pressing.
In this aspect, the planographic printing plate is partially moved by pressing force from the pressing member, and a portion of the planographic printing plate expands and enters the expansion permission section. Hence, expansion due to the movement of the planographic printing plate at the time of pressing is allowed by the expansion permission section. Thus, the surface side of the planographic printing plate is positively pressed and it is possible to form the sloped face even if the pressing force from the pressing member is small.
In a seventh aspect of the present invention, the cutting member cuts the planographic printing plate along an area within the recessed section of the planographic printing plate.
When cutting is done at a plurality of positions (areas) with respect to one recessed section, a portion between the cutting positions becomes chips. However, by cutting the planographic printing plate at one position with respect to one recessed section, such chips are not generated, and the planographic printing plate can be machined without wasting materials.
In an eighth aspect of the present invention, the planographic printing plate machining method includes a recessed section forming process for pressing and indenting a planographic printing plate from the surface on the printing side to form a recessed section which continues from this surface, and has a sloped face slanting with respect to the surface, and a cutting process for cutting the planographic printing plate at a predetermined cutting position.
In this planographic printing plate machining method, either of the recessed section forming process and the cutting process may be carried out first.
In a case wherein the recessed portion forming process is carried out first, thereof in the recessed section forming process, the planographic printing plate is pressed by the pressing member from the surface so that a recessed section which continues from the surface and has a sloped face slanting with respect to the surface, is formed at the planographic printing plate. Next, in the cutting process, the planographic printing plate is cut at the recessed section. As a result, one portion or the whole of the sloped face formed in the recessed section forming process remains at the planographic printing plate after the cutting process, and this remaining sloped face effectively forms a cutoff.
In contrast, in a case wherein the cutting process is carried out first, the planographic printing plate is first cut to a desired size at a predetermined cutting position. Next, the recessed section is formed by the recessed section forming process at a cut edge portion of the cut planographic printing plate. As a result, a sloped face; i.e. a cutoff, is formed at the edge portion of the planographic printing plate that is finally obtained.
Additionally, in the case wherein the cutting process is carried out first, a planographic printing plate machining device in accordance with, for example, the fifth aspect may be used. In other words, immediately after the cutting blade portion of the cutting press blade cuts the planographic printing plate in the cutting process, the recessed section can be formed with the recessed section forming section of the shearing press blade as the recessed portion forming process.
In this aspect, whichever of the recessed section forming process and the cutting process is carried out first, the formation of the cutoff and the cutting of the planographic printing plate are carried out in respectively separate processes. Thus, the cutting process is less susceptible to shearing drops at the time of forming the cutoff. In other words, it is possible to cut the planographic printing plate under conditions that can reduce shearing drops, and consequently to reduce burrs (and more preferably, to eliminate burrs). Moreover, because the sloped face is formed by the recessed portion forming process independently from the cutting process, it is possible to easily form a cutoff portion having a required size. In particular, even in the case of a planographic printing plate covered with a surface treatment layer containing, for example, an anode oxidation layer, it is possible to form a cutoff portion having a required size.
In a ninth aspect of the present invention, the planographic printing plate is provided with a printing surface and a recessed section having a sloped face that continues from said printing surface, and a sheared surface terminating said recessed section.
In the case of a planographic printing plate in accordance with this aspect, a desired shape is cut from the recessed section. Thus, of the sloped face of the recessed section, the portion inside the cut section remains to form the cutoff portion. Moreover, the planographic printing plate with the desired shape cut at the recessed section, can be cut under conditions that reduce shearing drops at the time of cutting. Consequently, it is possible to minimize burrs (and more preferably, to eliminate burrs). Because the formation of the sloped face and the cutting process are carried out separately, the planographic printing plate is formed with a cutoff portion having a required size.
Additionally, a planographic printing plate based on the ninth aspect can be machined and manufactured by a planographic printing plate machining method based on the eighth aspect. In the case wherein the recessed section forming process is carried out first, the requirement of cutting at the recessed section can be satisfied by taking into consideration the cutting position at the time of the cutting process. Moreover, in the case wherein the shearing process is carried out first, the requirement of cutting at the recessed portion is effectively satisfied by forming the recessed section at the cut edge portion in the recessed section forming process.
Furthermore, in the above aspects, the condition that the sloped face xe2x80x9ccontinuesxe2x80x9d is effectively satisfied as long as ink does not adhere at a boundary portion between the sloped face (i.e. the cutoff) and the surface of the planographic printing plate and does not cause any line-shaped stains (so-called edge stains) to be printed on a surface of printing paper. Therefore, in this regard, even in a case when, for example, steps, grooves, etc. are present between the surface of the planographic printing plate and the sloped face, if those steps and grooves are so small that edge stains due to those steps and grooves are not printed on the surface of printing paper, the condition of the present invention that the sloped face xe2x80x9ccontinuesxe2x80x9d is effectively satisfied.